Oil hydrodesulfurization with alumina composite catalyst utilizing aluminate and dicarboxylic acid in its preparation

ABSTRACT

A catalyst is provided which comprises a hydrogenation component composited with an alumina support prepared by reacting an alkali metal aluminate with an aliphatic dicarboxylic acid, e.g. oxalic acid.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a catalyst and process for hydrotreatingmineral oils. More particularly, this invention relates to a catalystcomprising a hydrogenation component composited with an alumina supportcharacterized by its method of preparation.

2. Description of the Prior Art

Hydrodesulfurization processes in which heavy hydrocarbon distillates orresidual fractions are hydrotreated with hydrogen in the presence of acatalyst comprising a hydrogenation component composited with arefractory oxide support, such as alumina, are well known. See, forexample, U.S. Pat. No. 3,531,389; U.S. Pat. No. 3,569,044 and U.S. Pat.No. 3,770,618.

Hydrotreating catalysts having specified physical characteristics, suchas pore size distribution, have been proposed to overcome thedisadvantages of conventional prior art catalysts.

U.S. Pat. No. 3,917,808 discloses a process for producing an aluminaextrudate by mixing alpha alumina monohydrate with a monoprotic acid anda polyprotic acid (including oxalic acid).

It has now been found that a hydrotreating catalyst comprising analumina carrier having specific characteristics resulting from itsmethod of preparation provides advantages that will become apparent inthe ensuing description.

The term "hydrotreating process" is intended herein to designate aprocess in which a hydrocarbon feed-stock is contacted with a catalystin the presence of hydrogen and under selected conditions to removeheteroatoms such as sulfur, nitrogen, oxygen and metallic contaminantssuch as nickel, vanadium and iron, from the feedstock and/or to saturatearomatic hydrocarbons and/or olefinic hydrocarbons in the feedstockand/or to hydrocrack the feedstock.

SUMMARY OF THE INVENTION

In accordance with the invention, there is provided, in a process ofhydrotreating a sulfur-containing hydrocarbon oil which comprisescontacting said oil at hydrotreating conditions with hydrogen and acatalyst comprising an alumina-containing support composited with ahydrogenation component, said hydrogenation component comprising asleast one Group VIB metal component and at least one Group VIII metalcomponent, the improvement which comprises said alumina having beenprepared by the steps which comprise reacting a solution of an aluminateselected from the group consisting of alkali metal aluminates andammonium aluminate with an aqueous solution of an aliphatic dicarboxylicacid.

In accordance with another embodiment of the invention, there isprovided a catalyst comprising an alumina-containing support compositedwith a hydrogenation component selected from the group consisting of atleast one Group VIB metal component and at least one Group VIII metalcomponent, said alumina having been prepared by the steps which comprisereacting a solution of an aluminate selected from the group consistingof alkali metal aluminates and ammonium aluminate with an aqueoussolution of an aliphatic dicarboxylic acid.

In accordance with another embodiment of the invention, there isprovided an alumina prepared by the steps which comprise: (a) reacting asolution of an aluminate selected from the group consisting ofalkali-metal aluminates and ammonium aluminate with an aliphaticdicarboxylic acid to produce a hydrous aluminum oxide, and (b) calciningthe hydrous aluminum oxide to produce alumina.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A sulfur-containing hydrocarbon feedstock is contacted in ahydrotreating zone with hydrogen and the catalyst of the presentinvention at hydrotreating conditions to produce a hydrocarbon producthaving a reduced content of sulfur. The process of the present inventionis particularly well suited for the hydrodesulfurization andhydrodemetallization of heavy sulfur-bearing mineral oils which usuallyalso contain a high content of metallic contaminants.

HEAVY HYDROCARBON FEEDSTOCKS

The heavy hydrocarbon feedstock utilized in the present inventioncomprises hydrocarbons boiling above 650° F. (343.33° C.) at atmosphericpressure which contain substantial quantities of material boiling above1,000° F. (537.78° C.). The process is particularly suited for treatingheavy crude mineral oils, residual petroleum oil fractions, such asfractions produced by atmospheric and vacuum distillation of crude oils.Such residual oils usually contain large amounts of sulfur and metalliccontaminants such as nickel and vanadium. The total metal content ofsuch oils may range up to 2,000 weight parts per million or more and thesulfur content may range up to 8 weight percent or more. The Conradsoncarbon residue of these heavy hydrocarbon feeds will generally rangefrom about 5 to about 50 weight percent (as to Conradson carbon residue,see ASTM test D-189-65). The preferred process feedstock is a petroleumresiduum obtained from distillation or other treating or separationprocess. From about 30 to about 100 percent of the petroleum residuumfeed boils above 900° F. (482.22° C.) at atmospheric pressure. Othersuitable feedstocks include heavy hydrocarbons recovered from tar sands;synthetic crude oils recovered from oil shales; heavy oils produced fromthe liquefaction of coal, and the like, and mixtures of any of thesefeeds. The hydrocarbon feeds will generally contain at least 10 percentof materials boiling above 1,000° F. (537.78° C.) (at atmosphericpressure).

OPERATING CONDITIONS IN THE HYDROTREATING ZONE

Suitable operating conditions in the hydrotreating zone are summarizedin the following table:

    ______________________________________                                                         Broad       Preferred                                        Conditions       Range       Range                                            ______________________________________                                        Temperature, ° F.                                                                       500-900° F.                                                                        650-800                                          Pressure, psig   600-3500    800-3200                                         Liquid hourly space                                                           Velocity, V/V/Hr.                                                                              0.05-5.0    0.10-2.5                                         Hydrogen Rate, SCF/bbl.                                                                        300-20,000  600-12,000                                       Hydrogen Partial Pressure                                                                      500-3000    800-2500                                         ______________________________________                                    

THE HYDROTREATING CATALYST

The hydrotreating catalyst of the present invention utilized in thehydrodesulfurization zone comprises a hydrogenation component and analumina-containing support. Commercially available alumina is typicallyprepared by neutralizing sodium aluminate with an aqueous solution ofsulfuric acid (H₂ SO₄) or Al₂ (SO₄)₃ or mixtures thereof. In accordancewith the present invention, instead of H₂ SO₄ or Al₂ (SO₄)₃, an aqueoussolution comprising an organic aliphatic dicarboxylic acid is used toneutralize an alkali metal aluminate or an ammonium aluminate andthereby precipitate a hydrous aluminum oxide. Preferably the aluminateused is sodium aluminate. Organic acids suitable for use in preparingthe alumina of the present invention include saturated aliphaticdicarboxylic acids, and unsaturated aliphatic dicarboxylic acids,preferably C₂ to C₆ dicarboxylic acids, such as ethanedioic acid (oxalicacid), propanedioic acid, butanedioic acid, and cisbutenedioic acid(maleic acid). The preferred dicarboxylic acid is ethanedioic acid(oxalic acid).

To prepare the alumina of the present invention an alkali metalaluminate or ammonium aluminate source is dissolved in water. Forsimplicity of description, the preparation of the alumina will bedescribed hereinafter with reference to sodium aluminate. Sodiumhydroxide may be added to promote the solubilization of the sodiumaluminate in the water. One method of obtaining a solution of sodiumaluminate is to dissolve alumina trihydrate in an aqueous solution ofsodium hydroxide so as to cause the following reaction to occur:

    Al.sub.2 O.sub.3.3H.sub.2 O + 2NaOH → 2NaAlO.sub.2 + 4H.sub.2 O

the molar ratio of NaOH to Al₂ O₃.3H₂ O may range from about 2:1 to 5:1,preferably from about 2:1 to 3:1. The molar ratio of water to aluminumtrihydrate ranges from the amount necessary to essentially completelysolubilize the sodium aluminate up to values of 500 or more moles ofwater per mole of aluminum trihydrate. To this sodium aluminate solutionis added a solution of ethanedioic acid (oxalic acid) so as to lower thepH to a range of about 7 to about 9, preferably from about 8.5 to about9. This addition may occur within a time interval of about 5 minutes orless to several hours at a temperature from ambient temperature (e.g.60° F.) up to the boiling point of the solution, preferably from about80° F. to about 150° F. The neutralization takes place according to theequation:

    2NaAlO.sub.2 + H.sub.2 C.sub.2 O.sub.4 + 2H.sub.2 O → 2Al(OH).sub.3 + Na.sub.2 C.sub.2 O.sub.4

desirably, the molar ratio of H₂ C₂ O₄ to alumina trihydrate will be atleast the theoretical ratio, that is, 1:1. The ratio may be higherdepending on the amount of excess NaOH added to the mixture.

The above prepared alumina, after washing, filtering, drying andcalcination at a temperature ranging from about 500° to about 1200° F.for a time period ranging from about 1 to about 24 hours, is compositedwith a hydrogenation component in a conventional manner, such as, forexample, by impregnation of the alumina with a solution of the desiredmetallic components. The metal-impregnated alumina is thereafter usuallycalcined and may be reduced and/or sulfided to convert the metalliccomponents to an active form. As previously stated, although sodiumaluminate was described as the aluminate utilized, other alkali metalaluminates or ammonium aluminate may be used as starting material.

The preferred hydrogenation component of the catalysts of the presentinvention is selected from the group consisting of at least oneelemental metal, metal oxide or metal sulfide of a Group VIB metal andat least one elemental metal, metal oxide or metal sulfide of a GroupVIII metal of the Periodic Table of Elements. The Periodic Tablereferred to herein is in accordance with the Handbook of Chemistry andPhysics published by the Chemical Rubber Publishing Company, Cleveland,Ohio, 45th edition, 1964. The preferred Group VIB metal component isselected from the group consisting of molybdenum oxide, molybdenumsulfide, tungsten oxide, tungsten sulfide and mixtures thereof and thepreferred Group VIII metal component is selected from the groupconsisting of nickel oxide, nickel sulfide, cobalt oxide, cobalt sulfideand mixtures thereof. The support of the catalyst is analumina-containing support, that is, the support is predominantlyalumina prepared as indicated above which may be composited with minoramounts of other inorganic oxides such as silica. Preferably, thesupport consists essentially of alumina.

When the catalyst contains metal oxide hydrogenation components, thecatalyst is preferably sulfided prior to use in a conventional way.

Suitable ranges of hydrogenation component include from about 5 to about30 weight percent, preferably from about 10 to about 30 weight percentof a Group VIB metal component, calculated as the metal oxide based onthe total catalyst, and from about 1 to about 15 weight percent,preferably from about 2 to about 10 weight percent of a Group VIII metalcomponent calculated as the metal oxide based on the total catalyst. Apreferred catalyst composition is as follows:

    ______________________________________                                                           Broad      Preferred                                       Catalyst Composition                                                                             Range      Range                                           ______________________________________                                        Nickel or cobalt (as oxide),                                                  wt. %              1 to 15     2 to 10                                        Tungsten or molybdenum                                                        (as oxide), wt. %  5 to 30    10 to 30                                        Alumina            Balance    Balance                                         ______________________________________                                    

The hydrogenation component can be composited with the alumina supportin a conventional manner, such as, for example, by impregnating aluminaprepared in accordance with the process of the present invention withsalts of the desired hydrogenation metals. The following examples arepresented to illustrate the invention.

EXAMPLE 1

A conventional catalyst, hereinafter to be designated catalyst A, wasprepared as follows:

A sodium aluminate solution was prepared first by dissolving 104 gramsof NaOH in 104 ml. of water. This solution was heated to 212° F. andthen 136 grams of Al₂ O₃.3H₂ O were added to it and the resulting slurrywas stirred until solubilization occurred. The resulting solution willhereinafter be designated solution I. In another container, 5500 ml. ofdeionized water were heated to 117° F. To this water, 3.4 ml. of a 50%gluconic acid (i.e. pentahydroxyhexoic acid) solution were added. Thissolution will hereinafter be designated solution II.

Solution I was then added to Solution II and thoroughly mixed. Theresulting solution will hereinafter be designated solution III.Neutralization was started by adding 865 ml. of a 7.5% H₂ SO₄ solution(95 ml. conc. H₂ SO₄ + 1900 ml. H₂ O) to solution III. This addition wasmade dropwise over a period of 27 minutes. The final pH of the resultingsolution was about 10.7. The neutralization was then completed by adding640 ml. of Al₂ (SO₄)₃ solution (358.4 grams Al₂ (SO₄)₃. 18H₂ O plus1641.6 grams H₂ O). This addition was made over a period of 33 minutesuntil the pH was between 8.8 and 9.0. An additional 87 ml. of a 10% NaOHsolution had to be added to maintain the pH above 8.8. The mixture wascooled and filtered. The recovered solid was washed with distilled waterand then spray dried. The alumina was then extruded and calcined for 3hours at 1000° F. The molybdenum oxide was incorporated by dissolving13.9 grams of ammonium heptamolybdate [(NH₄)₆ Mo₇ O₂₄.4H₂ O] in asufficient amount of water to make 53 ml. of solution. A small amount ofNH₄ OH was added for substantially complete solubility.

This addition was made by the incipient wetness technique to 75.7 gramsof the previously extruded alumina. After impregnation, the solidmaterial was dried and calcined 3 hours at 1000° F. Then 11.30 grams ofCo(NO₃)₂.6H₂ O were dissolved in a sufficient amount of water to make 53ml. of solution. This solution was added to the above preparedimpregnated and calcined solid material by the incipient wetnesstechnique. The resulting solid material was then dried in a vacuum ovenat 150° F. for 16 hours. The resulting catalyst (A) comprised 3.2 wt. %CoO and 12.6 wt. % MoO₃, the balance being Al₂ O₃. Prior to testing, thecatalyst was calcined for 3 hours at 1000° F. and sulfided with amixture of 10% H₂ S in H₂ at 750° F.

EXAMPLE 2

A catalyst, hereinafter to be designated catalyst B, was prepared inaccordance with the process of the present invention.

Catalyst B was prepared in an identical manner to that described forcatalyst A of Example 1, except that ethanedioic acid (oxalic acid) wasused as the neutralizing agent instead of the combination of H₂ SO₄ plusAl₂ (SO₄)₃. To a sodium aluminate mixture, prepared as in Example 1, asolution of 185 grams of ethanedioic acid dissolved in 2000 ml. of waterwas added at a rate of 30 ml. per minute until the pH was 8.8. The solidwas then filtered, washed, dried and calcined at 1000° F. The extrusionof the alumina and impregnation with catalytically active metals wereaccomplished in the same manner as that described in Example 1.

The resulting catalyst (B) comprised 3.2% CoO, 12.6 wt. % MoO₃, thebalance being Al₂ O₃. Prior to testing, the catalyst was calcined for 3hours at 1000° F. and sulfided with a mixture of 10% H₂ S in H₂ at 750°F.

The physical characteristics of catalysts A and B are shown in Table I.

                  TABLE I                                                         ______________________________________                                         PHYSICAL CHARACTERIZATION OF CATALYSTS                                       ______________________________________                                                       Catalyst A                                                                              Catalyst B                                           ______________________________________                                        Total Pore Volume,                                                            cm.sup.3 /g.     0.463       0.848                                            Total Surface Area, M.sup.2 /g.                                                                277         311.7                                            4 PV/SA           67         109                                              Pore Radius, A   cm.sup.3 /g.                                                                              cm.sup.3 /g.                                     ______________________________________                                        100,000-50,000   0.0000      0.0000                                           50,000-10,000    0.0011      0.0002                                           10,000-5,000     0.0007      0.0004                                           5,000-1,000      0.0014      0.0607                                           1,000-900        0.0001      0.0229                                           900-800          0.0001      0.0281                                           800-700          0.0002      0.0389                                           700-600          0.0002      0.0361                                           600-500          0.0003      0.0431                                           500-400          0.0004      0.0422                                           400-300          0.0006      0.0468                                           300-250          0.0004      0.0254                                           250-200          0.0006      0.0280                                           200-150          0.0029      0.0191                                           150-100          0.0112      0.0414                                           100-90           0.0056      0.0143                                           90-80            0.0085      0.0181                                           80-70            0.0138      0.0235                                           70-60            0.0230      0.0312                                           60-50            0.0435      0.0414                                           50-45            0.0341      0.0254                                           45-40            0.0476      0.0291                                           40-35            0.0553      0.0300                                           35-30            0.0552      0.0299                                           30-25            0.0543      0.0304                                           25-20            0.0513      0.0376                                           20-15            0.0508      0.1037                                           ______________________________________                                    

EXAMPLE 3

Catalysts A and B were utilized to hydrotreat a Cold Lake Crude oil at750° F., 2250 psig, at a space velocity of 1 V/V/Hr. and 6000 standardcubic feet of hydrogen per barrel of oil.

Results of these tests are summarized in Table II.

                  TABLE II                                                        ______________________________________                                        HYDROTREATING OF COLD LAKE CRUDE OIL AT                                       750° F., 2250 PSIG, 1 V/V/HR. AND 6000 SCF H.sub.2 /B                  ______________________________________                                        Catalyst           A            B                                             ______________________________________                                        % Removals                                                                     Sulfur            88.2         86.7                                           Nickel            66.2         86.9                                           Vanadium          68.2         96.2                                          2-K Rate Constants                                                            (V/V/Hr. Basis), hr.sup.-.sup.1                                                Sulfur            1.52         1.42                                           Nickel            0.52         1.43                                           Vanadium          0.58         2.62                                          Sulfur 1.5 Order K.sub.1                                                      (W/Hr./W Basis), hr..sup.-.sup.                                               ______________________________________                                    

As can be seen from the data in Table II, catalyst B, which is acatalyst in accordance with the present invention, showed ademetallization activity 2.8 and 4.5 times higher than the prior artcatalyst A for nickel and vanadium removal, respectively.

What is claimed is:
 1. In a process of hydrotreating a sulfur-containingheavy hydrocarbon oil to reduce the sulfur content thereof whichcomprises contacting said oil at hydrodesulfurization conditions withhydrogen and with a catalyst comprising alumina and hydrogenationcomponents composited with said alumina, said hydrogenation componentsare selected from the group consisting of at least one elemental metal,metal oxide and metal sulfide of a Group VI-B element of the PeriodicTable of Elements and at least one elemental metal, metal oxide andmetal sulfide of a Group VIII element of the Periodic Table of Elementsthe improvement which comprises said alumina having been prepared by thestep which comprises reacting a solution of an aluminate selected fromthe group consisting of alkali metal aluminates and ammonium aluminatewith an aqueous solution of an aliphatic dicarboxylic acid toprecipitate a hydrous aluminum oxide.
 2. The process of claim 1 whereinsaid dicarboxylic acid is selected from the group consisting of C₂ to C₆saturated aliphatic dicarboxylic acids and C₂ to C₆ unsaturatedaliphatic dicarboxylic acids.
 3. The process of claim 1 wherein saiddicarboxylic acid is selected from the group consisting of ethanedioicacid, propanedioic acid, butanedioic acid and cisbutenedioic acid. 4.The process of claim 1 wherein said dicarboxylic acid is ethanedioicacid.
 5. The process of claim 1 wherein said aluminate is sodiumaluminate.
 6. The process of claim 1 wherein after said aluminate isreacted with said aqueous solution of an aliphatic dicarboxylic acid,the resulting hydrous aluminum oxide is calcined at a temperatureranging from about 500° F. to 1200° F.
 7. The process of claim 1 whereinsaid hydrodesulfurization conditions include a temperature ranging fromabout 500° to 900° F. and a hydrogen partial pressure ranging from 500to 3000 psig.